Retinal imaging for reference during laser eye surgery

ABSTRACT

A method of laser eye surgery including linking retinal vessel architecture to corneal topography. This enables registration of the steep axis of the cornea in order to orient a toric intraocular lens, and/or to place astigmatic keratotomy incisions. First, a detailed pre-operative retinal image of the vasculature of the retina is obtained. In addition, a pre-operative image of the topography of the eye is obtained. The retinal image is then correlated or superimposed on the topography image to provide a reference. After the patient lies down under the laser eye surgery system, and during the surgery, the retinal vasculature is monitored which provides a reference to the surgery system about the topography of the eye. This process enables registration of the steep axis of the cornea in order to orient a toric intraocular lens and/or to place astigmatic keratotomy incisions.

RELATED APPLICATIONS

This application claims priority to, and the benefit of, under 35 U.S.C.§119(e) of U.S. Provisional Appl. No. 62/359,014, filed Jul. 6, 2016,which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present application pertains to laser-assisted eye surgery and, moreparticularly, to methods of orienting a laser optical system to anastigmatic eye by pre-operative retinal imaging.

BACKGROUND

A cataract is formed by opacification of the crystalline lens or itsenvelope—the lens capsule—of the eye. The cataract obstructs passage oflight through the lens. A cataract can vary in degree from slight tocomplete opacity. Early in the development of an age-related cataract,the power of the lens may be increased, causing near-sightedness(myopia). Gradual yellowing and opacification of the lens may reduce theperception of blue colors as those wavelengths are absorbed andscattered within the crystalline lens. Cataract formation typicallyprogresses slowly resulting in progressive vision loss. If leftuntreated, cataracts may cause blindness.

Several commercial laser-assisted eye surgery systems are available tofacilitate cataract removal and astigmatism correction. The CATALYSPrecision Laser System from Abbott Medical Optics is indicated foranterior capsulotomy, phacofragmentation, and the creation of singleplane and multi-plane arc cuts/incisions in the cornea to correctastigmatism. The CATALYS System uses a two-piece liquid-filled interfacethat docks with the patient's eye and provides a clear optical path forreal-time video, OCT imaging, and laser treatment. Other systems forlaser cataract surgery are the LenSx Laser from Alcon Laboratories,Inc., the LENSAR Laser System from LENSAR, Inc., and the VICTUSFemtosecond Laser Platform from TECHNOLAS Perfect Vision GmbH, aBausch+Lomb Company.

Another laser procedure is laser-assisted in situ keratomileusis(“LASIK”). which is a refractive surgery that treats the cornea of theeye to correct myopia, hyperopia, and/or astigmatism. Since thisprocedure involves treatment within corneal tissue. it requires a “flap”to be created and lifted to expose a middle section of the cornea (the“stroma”) for photoablation with an excimer laser. Previously, surgicaltools such as microkeratomes were used to create corneal flaps. But,these clays, flaps are created and prepared using a non-ultraviolet,ultra-short pulsed laser that emits radiation in ultra-short pulsedurations measured in as few as a few femtoseconds or a few nanoseconds.Examples of ultra-short pulsed laser systems include the Abbott MedicalOptics iFS Advanced Femtosecond Laser, the Intralase FS Laser, as wellas various other femtosecond and picosecond lasers available in themarket.

One challenge during laser eye surgery is maintaining a preciseunderstanding of the geography of the astigmatic patient's eye,especially between the stages where the patient is upright and supine onthe treatment table. Presently, there are a number of ways for measuringthe eye for proper alignment of toric intraocular lenses, incisionalcorrection of astigmatism and laser application to the cornea.Typically, surgeons place marks on the eye using a surgical marking pento serve as a reference point for alignment of toric intraocular lensesand other therapeutic applications such as making corneal incisions.Other imaging modalities exist for keeping track of the astigmatic eyeduring the surgery, including topography, ocular coherence tomography(OCT), wavefront sensing (including Marie Talbot interferometry used inWaveTec ORA), and video photography. None of these techniques is 100%accurate, and the need for continuous real-time monitoring of theposition of the eye interferes with an efficient procedure.

Accordingly, there is a need for a simpler and more accurate way toconvey the orientation and position of the eye to the laser surgerysystem.

SUMMARY

The present disclosure solves a number of deficiencies in priortechniques for monitoring the orientation and position of the eye duringlaser eye surgery. The method involves obtaining a pre-operative imageof the terrain of the retina to which is then calibrated with anunderstanding of the topography of the eye. Subsequently, theregistration between the retinal image and topography enables the laserto adapt to changing positions and orientations of the patient's eyeduring the surgery.

The methods disclosed herein involve linking retinal vessel architectureto corneal topography. This enables registration of the steep axis ofthe cornea in order to orient a toric intraocular lens and/or to placeastigmatic keratotomy incisions.

The methods include use of retinal landmarks as reference marks forocular alignment. The retinal landmarks would be determined from retinalimages obtained preoperatively (before the surgery) and intraoperative(during surgery). Computer analysis would be conducted on the images todetermine a misalignment measurement that a surgeon would use as a guidein placing the therapeutic product (e.g. IOL).

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIG. 1 is a perspective view showing an exemplary laser eye surgerysystem; and

FIG. 2 is a schematic diagram of methods disclosed herein for linkingretinal vessel architecture with corneal topography.

DETAILED DESCRIPTION

FIG. 1 shows an exemplary laser eye surgery system 2 operable to formprecise incisions in the cornea, in the lens capsule, and/or in thecrystalline lens nucleus. The methods described herein can be performedin conjunction with use of the laser eye surgery system 2 for a betterand more accurate understanding of the location of the steep axis of thecornea in order to orient a toric intraocular lens and/or to placeastigmatic keratotomy incisions.

The system 2 includes a diagnostic and interventional unit 4, a patientchair 6, a dual function footswitch 8, and a laser footswitch 10. Thediagnostic and interventional unit 4 houses many primary subsystems ofthe system 2. For example, externally visible subsystems include atouch-screen control panel 12, a patient interface assembly 14, patientinterface vacuum connections 16, a docking control keypad 18, a patientinterface radio frequency identification (RFID) reader 20, externalconnections 22 (e.g., network, video output, footswitch, USB port, doorinterlock, and AC power), laser emission indicator 24, emergency laserstop button 26, key switch 28, and USB data ports 30. The emergency stopbutton 26 can be pushed to stop emission of all laser output, releasevacuum that couples the patient to the system 2, and disable the patientchair 6. The stop button 26 is located on the system front panel, nextto the key switch 28. Although not shown, a processor and memory areassociated with the system 2 to provide precise control over a laserbeam that passes through the patient interface assembly 14 to operate ona patient's eye.

The patient chair 6 includes a base 32, a patient support bed 34, aheadrest 36, a positioning mechanism (internal, not shown), and apatient chair joystick control 38 disposed on the headrest 36. Thepositioning control mechanism is coupled between the base 32 and thepatient support bed 34 and headrest 36. The patient chair 6 isconfigured to be adjusted and oriented in three axes (x, y, and z) usingthe patient chair joystick control 38. The headrest 36 and a restrainsystem (not shown, e.g., a restraint strap engaging the patient'sforehead) stabilize the patient's head during the procedure. Theheadrest 36 includes an adjustable neck support to provide patientcomfort and to reduce patient head movement. The headrest 36 isconfigured to be vertically adjustable to enable adjustment of thepatient head position to provide patient comfort and to accommodatevariation in patient head size.

The dual function footswitch 8 is a dual footswitch assembly thatincludes the left foot switch 40 and a right foot switch 42. The leftfoot switch 40 is the “chair enable” footswitch. The right footswitch 42is a “vacuum ON” footswitch that enables vacuum to secure a liquidoptics interface suction ring to the patient's eye. The laser footswitch10 is a shrouded footswitch that activates the treatment laser whendepressed while the system is enabled.

The patient chair 6 is equipped with a “chair enable” feature to protectagainst unintended chair motion. The patient chair joystick 38 can beenabled in either of two ways. First, the patient chair joystick 38incorporates a “chair enable” button located on the top of the joystick.Control of the position of the patient chair 6 via the joystick 38 canbe enabled by continuously pressing the “chair enable” button.Alternately, the left foot switch 40 of the dual function footswitch 8can be continuously depressed to enable positional control of thepatient chair 6 via the joystick 38.

One of the challenges is that when the patient goes from the uprightpreoperative environment to being supine on the surface of patient chair6 during the procedure, some re-orientation of the eye is commonrelative to the position/orientation of the cranium, for example, andthe surgeon must find a way to re-establish his understanding of theorientation of the eye anatomy relative to the interventional tools.Conventionally, the physician will conduct a preoperative examinationwith the patient in an upright position, and will make a series of markswith a pen upon the cornea and/or sclera to provide a temporaryreference with regard to the astigmatic axis of the subject eye; thisaxis may be subsequently utilized during surgery when the patientreclines to place relaxing cuts, radial cuts, or other types ofincisions, to tailor the geometry of capsular cuts, etc. Alternatively,a series of fidicual features and/or markers placed within the field ofview of the imaging system to view the eye anatomy may be used toestablish the eye orientation. These techniques have proved successful,but are not 100% accurate.

The present application contemplates a different methodology forpreoperative examination which is then used to keep track of the steepaxis of an astigmatic eye during the surgery, or other abnormalities.The method comprises imaging the retina as well as measuring thetopography of the eye and combining the information so that knowledge ofone will provide knowledge of the other. The method uses known, staticretinal landmarks as reference marks for ocular alignment.

FIG. 2 schematically illustrates the calibration scheme. The physicianor technician obtains an image of the retinal vessel architecture oroptic nerve, as seen on the right, preferably using a high-resolutionvideo camera. The retina features an intricate and static vasculaturewhich provides a detailed reference map. The retinal images obtainedduring the pre-operative workup are registered in the system memory. Atthe same time (simultaneously or immediately thereafter) that theretinal image is obtained, a scan of the corneal topography is made suchas with ocular coherence tomography (OCT). The two images are thencorrelated so that an understanding of the retinal image provides areference for the corneal topography, and vice versa. Normally thesepre-operative measurements are made with the patient sitting up, or atleast not lying down under the laser surgery system.

After preparing the patient, he or she is positioned supine under thelaser surgery system. Prior to conducting any procedure, the retina isimaged again, preferably with a high-resolution video camera. The secondretinal image obtained intraoperatively enables the system to analyzethe retinal vasculature and/or optic nerve to gauge misalignment of theeye (or head) compared to the pre-operative measurement. The system thenalerts the surgeon of the misalignment and recommends rotation of theeye (head) in a specific direction (clockwise or counter-clockwise) andby a specific amount (in degrees or radians) to properly align the eyewith the pre-operative measurements. Because the orientation of the eyeis known and the orientation of a therapeutic modality is known (i.e.,toric intraocular lens or arcuate keratotomies), a guide in the systemcan then provide feedback to the surgeon as to where to align thetherapeutic modality.

In laser surgeries, the information obtained regarding the retinalimages obtained both pre- and intra-operatively along with thetopographical scan of the eye are all stored in a memory of the lasersurgery system. Software may be coded to automatically correlate thepre-operative retinal image to the topography, and also compare the pre-and intra-operative retinal images. The software may simply alert thesurgeon as to any misalignment between the two retinal images, or mayinitiate an adjustment to the surgery system, such as rotation of apatient chair or control of the operating laser (e.g., such as during akeratotomy procedure).

Also, because of the pre-registration of the retinal image with thecorneal topography, further measurements of the topography are notneeded. Understanding of the retinal image once the patient is lyingdown can be translated into knowledge of the topography. Various lasereye surgery systems use different real-time imaging technology,typically OCT or Scheimpflug imaging. Precise control of the laser isinformed by an understanding of the corneal topography, supplied byreal-time retinal imaging. Preferably, the retina is imaged periodicallyduring the procedure to adapt to any further patient movements.

A typical adjustment provided by the methods described herein isaligning the cuts made by the laser eye surgery system with a tiltedsteep axis of the cornea. The precise misalignment of the cornea asobtained by the retinal imaging in conjunction with topographicalscanning guides a surgeon and proper placement of whatever therapeuticproduct or device is being applied to the eye. The guide could be acalculated measurement (i.e., degrees clockwise or counterclockwisemisalignment) or can be incorporated to guide a surgeon to rotate theeye (or the head) a specific direction to gain proper alignment.Alternatively, the guide could be used to place a product or device(i.e., a toric intraocular lens) a specific amount for proper alignment.

One particular guide that may be useful is to place a reticle in theoperating microscope to indicate toric intraocular lens alignment (orother therapeutic modalities) once the proper head position is verifiedwith the system. The reticle can be a series of fine lines or fibers inthe eyepiece of the microscope that indicates the steep axis of thecornea, or other characteristic misalignment. Insertion of toricintraocular lenses thus also may benefit from use of the presentmethodology, though the ultimate steps in the procedure do not involve alaser, but are rather manually accomplished.

Another application of the methodology disclosed herein is inregistering and aligning laser therapy to the cornea, including Excimerablations or laser-based arcuate keratotomies or other cornealincisions.

In general, the present eye registration methods are useful in a varietyof ophthalmic procedures, with or without using a laser. Exemplary lasersurgeries include cataract surgery, ablation of the cornea, orkeratotomy, and the like. Laser systems including excimer lasers such asthe Abbott Medical Optics' STAR S4 IR System, as well as femtosecondlasers such as the CATALYS Precision Laser System, and the intralase FSLaser may incorporate the techniques described herein. As mentionedabove, insertion of a toric IOL will also be facilitated with knowledgeof the steep meridian axis of the astigmatic eye provided by the retinalimaging and calibration, which does not involve a laser at all.

As mentioned above, a preferred method of retinal imaging ishigh-resolution videography or photography. However, other methods forretinal imaging are known, such as OCT, Zeiss scanners, and the like.High-resolution photography provides the greatest accuracy.

It should also be mentioned that the present application not only mayprovide a guide for rotational misalignment of the eye, such as with anastigmatic eye, but may also accommodate for translational movementduring surgery. Consequently, the intraoperative adjustment may includea rotational and a translational component.

Finally, redundant observations may be made of secondary anatomicalfeatures of the eye to provide a check on the retinal imaging methodsdescribed above. For instance, iris and/or sclera landmarks may be notedin the pre-operative phase and referenced to the retinal image ortopographical scan. Such secondary references may then be checkedintra-operatively, along with the retinal image calibration, to ensurethat they agree. If there is some discrepancy, the procedure may behalted and repeated. Of course, the preferred method is to use theretinal imaging which provides a highly detailed reference map of theeye with which to register the steep meridian axis of the astigmaticeye.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. It should be understoodthat various alternatives to the embodiments of the invention describedherein may be employed in practicing the invention. It is intended thatthe following claims define the scope of the invention and that methodsand structures within the scope of these claims and their equivalents becovered thereby.

What is claimed is:
 1. A method of eye surgery on an astigmatic patient,comprising: pre-operatively obtaining a first retinal image of theretinal vessel architecture or optic nerve; pre-operatively scanning thecorneal topography of the patient to obtain a scan; correlating thefirst retinal image and scan to determine retinal landmarks associatedwith an astigmatic axis of the patient; recording the location of theretinal landmarks in an optical system of an eye surgery system used forthe eye surgery; positioning the patient supine on a chair configuredfor the eye surgery; obtaining a second retinal image of the retinalvessel architecture or optic nerve while the patient is positioned onthe chair; analyzing the second retinal image to gauge a misalignment ofthe eye compared to the first retinal image; adjusting the patient oreye surgery system based on the misalignment and correlation of thefirst and second retinal images and scan; and performing an eye surgery.2. The method of claim 1, wherein the eye surgery is insertion of atoric intraocular lens, and the step of recording includes placing areticle in the optical system.
 3. The method of claim 1, wherein the eyesurgery is insertion of a toric intraocular lens, and the step ofadjusting the patient includes rotating the patient in the chairrelative to the optical system.
 4. The method of claim 3, wherein thestep of adjusting the patient further includes translating the patientin the chair relative to the optical system.
 5. The method of claim 1,wherein the eye surgery is cataract removal using a laser eye surgerysystem and intraocular lens replacement, and the step of recordingcomprises storing the retinal landmarks in a system memory of the lasereye surgery system.
 6. The method of claim 1, wherein the eye surgery iskeratotomy using a laser eye surgery system, and the step of recordingcomprises storing the retinal landmarks in a system memory of the lasereye surgery system.
 7. The method of claim 6, wherein the step ofadjusting the laser eye surgery system includes aligning cuts made bythe laser eye surgery system with a tilted steep axis of the cornea. 8.The method of claim 1, wherein the step of pre-operatively obtaining afirst retinal image and obtaining a second retinal image are bothperformed with a high-resolution camera.
 9. The method of claim 1,wherein the step of pre-operatively scanning the corneal topography isperformed using ocular coherence tomography (OCT).
 10. The method ofclaim 1, wherein the method does not include scanning the cornealtopography after the step of pre-operatively scanning the cornealtopography.
 11. A method of eye surgery on an astigmatic patient,comprising: pre-operatively obtaining a first retinal image of theretinal vessel architecture or optic nerve; storing the first retinalimage in a system memory of a laser eye surgery system having software;pre-operatively scanning the corneal topography of the patient to obtaina scan; correlating the first retinal image and scan to determineretinal landmarks associated with an astigmatic axis of the patient andstoring the correlation in the system memory; positioning the patientunder the laser eye surgery system; obtaining a second retinal image ofthe retinal vessel architecture or optic nerve while the patient ispositioned under the laser eye surgery system; analyzing the secondretinal image to gauge a misalignment of the eye compared to the firstretinal image stored in system memory; alerting the system software ofany misalignment; adjusting the patient or laser eye surgery systembased on the misalignment and correlation of the first and secondretinal images and scan; and performing an eye surgery.
 12. The methodof claim 11, wherein the wherein the eye surgery is insertion of a toricintraocular lens, and the step of recording includes placing a reticlein an optical system of the laser eye surgery system.
 13. The method ofclaim 11, wherein the eye surgery is insertion of a toric intraocularlens, and the step of adjusting the patient includes rotating thepatient in a chair configured for the eye surgery relative to an opticalsystem of the laser eye surgery system.
 14. The method of claim 13,wherein the step of adjusting the patient further includes translatingthe patient in the chair relative to the optical system.
 15. The methodof claim 11, wherein the eye surgery is cataract removal and intraocularlens replacement.
 16. The method of claim 11, wherein the eye surgery iskeratotomy using a laser eye surgery system.
 17. The method of claim 16,wherein the step of adjusting the laser eye surgery system includesaligning cuts made by the laser eye surgery system with a tilted steepaxis of the cornea.
 18. The method of claim 11, wherein the step ofpre-operatively obtaining a first retinal image and obtaining a secondretinal image are both performed with a high-resolution camera.
 19. Themethod of claim 11, wherein the step of pre-operatively scanning thecorneal topography is performed using ocular coherence tomography (OCT).20. The method of claim 11, wherein the method does not include scanningthe corneal topography after the step of pre-operatively scanning thecorneal topography.